cHAr. XXII THE FLORA OF NEW ZEALAND 505 



with these indigenous and well-estabhshed plants, and only 

 in a few cases were able to obtain a footing; whence it 

 arises that we have many Australian types, but few 

 Australian species, in New Zealand, and both phenomena 

 are directly traceable to the combination of great powers of 

 dispersal with a high degree of adaptability. Exactly the 

 same thing occurs with the still more highly specialised 

 Orchidese. These are not proportionally so numerous in 

 New Zealand (about forty species), and this is no doubt 

 due to the fact that so many of them require insect- 

 fertilisation often by a particular family or genus (whereas 

 almost any insect will fertilise Compositse), and insects of 

 all orders are rather scarce in New Zealand.^ This would 

 at once prevent the establishment of many of the orchids 

 which may have reached the islands, while those which 

 did find suitable fertilisers and other favourable conditions 

 would soon become modified into new species. It is thus 

 quite intelligible why only three species of orchids are 

 identical in Australia and New Zealand, although their 

 minute and abundant seeds must be dispersed by the 

 wind almost as readily as the spores of ferns. 



Another specialised group — the Scrophularineae— 

 abounds in New Zealand, where there are about seventy 

 species ; but though almost all the genera are Australian 

 only three species are so. Here, too, the seeds are usually 

 very small, and the powers of dispersal great, as shown by 

 several European genera — Veronica, Euphrasia, and Limo- 

 sella, being found in the southern hemisphere. 



Looking at the whole series of these Australo-New 

 Zealand plants, we find the most highly specialised 

 groups — Compositse, Scrophularineae, Orchidese — with a 

 small proportion of identical species (one-thirteenth to one 

 twentieth), the less highly specialised — Eanunculaceae, 

 Onagrarise and Ericea? — with a higher proportion (one- 

 ninth to one-sixth), and the least specialised — Juncese, 



^ Insects are tolerably abundant in the open mountain regions, but very 

 scarce in the forests. Mr. Meyrick says that these are " strangely deficient 

 in insects, the same species occurring throughout the islands ; " and Mr. 

 Pascoe remarked that ' ' the forests of New Zealand were the most barren 

 country, entomologically, he had ever visited." {Proc. Ent. Soc, 1883. p. 

 xxix, ) 



